The specific aims of this project are to collect data at three, four, and five years relevant to the clinical performance of six amalgam alloys (Dispersalloy, Tytin, Sybraloy, Caulk's Spherical, Velvalloy, and Indiloy). Each alloy was placed in fifty patients in 1978 in highly controlled clinical studies at Oral Roberts University and at the University of the Pacific. Three different clinical evaluation methods (the U.S.P.H.S. criteria, the Mahler method, and the stereo-photogrammetric method developed by Eick) will be used and data obtained from each method will be compared. A variety of statistical methods will be applied to the data to evaluate clinical performance between alloys, clinical performance between study sites, and to explore the difference between "statistical significance" and "clinical" significance. The accuracy, efficiency, expediency, and cost effectiveness of each of the three clinical evaluation methods will be compared. A computer will be used extensively to analyze the data. Improvement in the precision and efficiency of the stereo-photogrammetric system will be obtained by interfacing the stereo-photogrammetric plotter and an HP 9825 computer with digital readout attachments directly to the University computer. Of primary importance will be to determine if the stereo-photogrammetric method can be used to predict the long-term (five year) clinical performance of amalgam restorations in a relatively short time period (one to two years). The ultimate goal of this project will be to provide a model for future clinical studies involving dental amalgam, involving suggestions for appropriate sample size, placement criteria, evaluation method, statistical analysis, and duration of the study.